Check valves are used in piping systems, frequently with a pump. When a pump is started, the fluid the pump is pumping can build up pressure in the space downstream of the pump. In order to prevent a sudden rush of fluid into the remainder of the piping system that may cause a pressure surge, a check valve can slowly open to allow fluid to pass through the valve and into the remainder of the piping system. When a pump is shut off, the flow velocity can change rapidly and cause a pressure surge, including a reverse fluid flow back through the valve. The fluid downstream of a pump is ordinarily at a higher pressure than fluid upstream of the pump. Therefore, upon a failure of the pump, such as due to loss of power, the fluid will start to back flow through the piping system. Back flow through a piping system can lead to numerous problems, such as back driving a pump or contaminating upstream fluid or upstream piping components.
Accordingly, there is a need for valve that can allow fluid to flow into a piping system upon reaching a desired pressure, as well as a valve that can prevent back flow of fluid, such as due to a pump failure.